Automotive vehicle horns of the acoustic type comprise, in general, a linear electromagnetic motor mechanically coupled with a sound generating diaphragm which is acoustically coupled with the air column of a sound projector, typically of the convaluted or sea shell type. The motor is mounted within a housing and the circular diaphragm is mounted on the housing with its periphery in sealing engagement therewith to provide a chamber containing the motor. A projector is also mounted on the housing and the inlet and thereof is typically seated against the periphery of the diaphragm and is in sealing engagement therewith. The electromagnetic motor is adapted to be energized from the vehicle battery and includes switching contacts. When the motor is connected with the battery, as by closing a horn switch, the switch contacts are opened and closed by motion of the plunger which vibrates the diaphragm to generate sound energy.
It is well known that the motor chamber of this type of horn must be vented to the atmosphere in order to prevent overheating of the motor, especially when the motor is operated over relatively long periods. The overheating results from the heat dissipated by the motor itself within the chamber and also from the pumping action of the air contained within the chamber. In order to prevent such overheating, it is common practice to provide a vent passage between the motor chamber and the atmosphere.
Heretofore, the known venting arrangements have not been entirely reliable and have been relatively costly to incorporate in the horn structure.
In the Frigo U.S. Pat. No. 4,267,552 granted May 12, 1981, the motor chamber is vented by shaping the edge of the diaphragm so that it is provided with mutually orthogonal straight edges closely approaching the inner diameter of the flange of the housing thus providing a vent opening at each straight edge. In an alternative embodiment, the mounting flange of the housing which is crimped against the diaphragm is provided with diaphragm confronting channels which provide a vent path around the edge of the diaphragm.
In the vehicle horn of the Warnod U.S. Pat. No. 4,116,158 granted Sept. 26, 1978, the venting arrangement is provided at the peripheral mounting flange of the housing which receives the periphery of the diaphragm. In this arrangement, a gasket is interposed between the diaphragm and the flange and comprises a material which will prevent the ingress of water but will permit the passage of air.
The Neese U.S. Pat. No. 4,441,099 granted Apr. 3, 1984, discloses a vehicle horn in which the motor chamber is vented to the atmosphere through a passage formed in that portion of the plunger which confronts and extends through the diaphragm at the central opening therein.
A general object of this invention is to provide an improved venting arrangement for the motor chamber of a vehicle horn which will overcome certain disadvantages of the prior art.